We hereby claim foreign priority benefits under Title 35, United States Code, xc2xa7119, of the following foreign application for patent: Japanese Patent Application No. 123288, filed Apr. 30, 1999.
1. Technical Field
The present invention relates to a disk apparatus provided with a rotatable disk, which is a data recording medium, a head/slider that flies above the surface of the disk to read/write data therefrom/thereon in without making contact therewith, a head gimbal assembly (HGA) provided with a load beam on which wires for transmitting data are laid, and an actuator for holding the HGA and moving it in the radial direction of the disk. More particularly, the invention relates to a method for improving the HGA structure for laying wires, a wire forming method, and a wire forming apparatus.
2. Description of the Related Art
In a data recording medium such as a disk apparatus, a disk is rotated by a spindle motor and a head/slider is supported by an HGA. The head/slider is obtained by embedding a head (e.g., an MR head) for reading/writing data from/onto the surface of the disk. The slider flies above the rotating disk with the aid of an air bearing surface. The HGA, provided for each disk surface, is held by the actuator that rotates with respect to the frame of the disk apparatus and moved in the radial direction of the disk.
The HGA is provided with a load beam supported by the actuator at its rear end, a flexure attached close to front end of the load beam, a head/slider held at the flexure, and a conductive wire for transmitting data. The head/slider is attached to the flexure so as to enable an air bearing action to be generated by its pitching and rolling actions. Four wires will be provided for the HGA if the head is an MR one. Each of those wires is supported by an insulating material. One end of each wire is connected to an electrode pad of the head. This wire transmits data read by the head from a disk, or written by the head on the disk.
The HGA has a wiring configuration that is sometimes referred to as an over-the-top-looping type structure. In the case of such over-the-top-looping HGA, the head/slider is held at one surface of the load beam (head supporting surface) and each wire extended from the head connecting point passes through an aperture formed close to the front end of the load beam, then fixed on the other surface of the load beam (wire laying surface) at a wire fixing point between the head connecting point and the rear end of the load beam.
Each of the four wires forms a wire loop in a section between the head connecting point and the wire fixing point. For such an HGA, forming of the wire loop is indispensable so as to enable all the four wires to apply their bias pressures to the head/slider evenly. In order to achieve this, therefore, one end of each wire is connected to the head and an intermediate portion of the wire is fixed at the wire fixing point so as to form a wire loop as described above. The height of the wire loop from the wire laying surface of the load beam (hereafter, to be referred to as the wire height) is suppressed low and wire forming is always applied to each wire loop as described above.
FIG. 16 shows an example of the conventional wire forming in such the HGA. In FIG. 16,(a) and (b) are top views of the HGA in such a wire forming process. FIGS. 16(d) and 16(e) are cross sectional views of the HGA in correspondence to (a) and (b). FIG. 16(c) is also a cross sectional view of a wire forming pin 91 at the A-Axe2x80x2 line (see (a)).
The HGA has a load beam 20, a flexure 30, a head/slider 40, and a wire cable consisting of four wires 61. An aperture 28 is formed close to the front end of the load beam 20 and the four wires 61 extended from the head connecting point edge H are passed through the aperture 28 and fixed at the wire fixing points F1 and F2 on the wire laying surface 21 of the load beam 20. Each wire loop 610f is formed in a section between the head connecting point edge H and each of the wire fixing points F1 and F2.
The wire forming pin 91 is tapered from the rear side 91a towards the front side 91b. The wire forming pin 91 thus has tapering surfaces 91c and 91d on both sides thereof, which are tapered towards the bottom surface 91f. This wire forming pin 91 is structured so that its bottom surface 91f comes in contact with the load beam 20 and the its front surface 91b comes to the side of the front end 24 of the load beam 20 as shown in FIG. 16(a) and FIG. 16(d).
The wire forming pin 91 structured as shown in FIG. 16(a) and FIG. 16(d) is moved towards the head connecting point edge H from the wire fixing point F(F1 and F2), thereby the end portion formed by the front surface 91b and the tapering surfaces 91c and 91d is put in contact with the wire loop 610f. While the wire loop 610f is widened more to the right and left sides, therefore, the wire loop 610f is moved towards the head connecting point edge H so as to deform the section close to the head connecting point edge H of the wire loop 610f plastically as shown in FIG. 16(b) and FIG. 16(e).
In the case of such the conventional HGA, however, a stress is concentrated on the wire positioned at the head connecting point edge H side in the wire forming process. And, if the difference between stresses applied at the front and at the rear of the wire forming pin is increased, the wire, trying to keep the balance of its force, goes away towards the rear of the wire forming pin. The wire is thus loosened in a section between a portion (a driving portion) to which a force is applied by the wire forming pin and the wire fixing point F, thereby the wire loop cannot be deformed enough plastically sometimes.
FIG. 17 is an example of a cross sectional view of the conventional HGA after its wire loop forming is ended. FIG. 17 is equivalent to the cross sectional view at the B-Bxe2x80x2 line in FIG. 16(i b). In FIG. 17, the wire loop 610fb, which is one of the four wire loops (610fa, 610fb, 610fc, and 610fd), is not deformed enough plastically and this wire loop 610fb causes the wire height HWf from the load beam 20 to be increased. The wire height HWf is the maximum height of the four wire loops 610f from the wire laying surface 21.
If the wire height cannot be reduced because of insufficient plastic deformation of the wire loop, the HGA clearance from the disk apparatus housing is reduced. If the disk apparatus includes a plurality of disks, the clearance between HGA""s is also reduced. In addition, if a variation of plastic deformation is generated among wire loops, the bias pressure of each wire is also varied from others, causing the static attitude of the head/slider to become unstable. The static attitude of the head/slider means a position of the head/slider taken with respect to the load beam while the head/slider does not fly above the surface of the disk.
The conventional HGA wire laying structure has such problems that must be solved in order to further reduce the structure of the disk apparatus in thickness, as well as further stabilize the static attitude of the head/slider.
The head gimbal assembly (HGA) of the present invention is provided with a slider that flies above the surface of a disk, and a head for reading/writing data from/onto the surface of the disk. One or more conductive wires are connected to the head and are used to transmit data. A load beam supports the wire(s) thereon and holds the head/slider near a front end of the load beam. The rear end of the load beam is supported by an actuator. Each of the wires is fixed at a point between the head connecting point edge and the rear end on the surface of the load beam. Each wire also forms a wire loop between the head connecting point edge and the wire fixing point. The distance between the head connecting point and the wire fixing point is set to about 2.7 to 3.8 mm.
In addition, the wire forming method applied for the HGA of the present invention includes a step for compressing a predetermined portion of each wire loop from above on the surface of the load beam, and a step for protruding the predetermined compressed portion towards the head connecting point edge, thereby plastically deforming a section between the head connecting point edge and the predetermined portion of the wire loop.
Furthermore, the HGA wire forming apparatus of the present invention is provided with means for moving a wire forming pin down onto the surface of the load beam, thereby letting the wire forming pin come in contact with a predetermined portion of the wire loop and compressing the predetermined portion, and means for rotating the wire forming pin that has compressed the predetermined portion towards the head connecting point edge, thereby extruding the predetermined portion towards the head connecting point edge.
Therefore, it is an object of the present invention to provide a wire laying structure for the HGA, which allows the wire height from the load beam to be reduced easily and surely.
It is another object of the present invention to provide a wire laying structure of the HGA, which allows the static attitude of the head/slider to be stabilized easily and surely.
It is an additional object of the present invention to provide an HGA wire forming method, which can allow the wire height to be reduced and stabilize the static attitude of the head/slider, as well as a wire forming apparatus that employs the method.
The above as well as additional objects, features, and advantages of the present invention will become apparent in the following detailed written description.